Electric discharge tube



May 7, 1929. v F, SKAUPY 1,712,407

ELECTRIC DISCHARGE TUBE Filed Aug. 50, 1921 F'Lgl. Figi.

Im/evrwtori Franz kaupg,

b9 HLAttorneg.

Patented May 7, 1929.

UNITED STATES PATENT OFFICE.

EEANz sxAUrY, or BERLIN, GERMANY, AssIeNon, EY MEsNE ASSIGNMENTS, :no GENERAL ELECTRIC COMPANY, oF scHENEcTAnY, NEW Yoan, A comenzaron or NEW YORK.

ELECTRIC DIQCHARGE 'll'."U'IBE4 Application led August 30, 1921, Serial No. 497,028, and in Germany July 4, 1919.

This invention relates to discharge tubes which operate with a glow discharge andmay be used for illumination purposes (as anlainp with glow discharge) or in the transmission of intelligence (as a vacuum tube for 1nstance) or for similar 'purposes and which can be run with an exceptionally low voltage without necessitating the use of electropositive metals for the cathode, or which, in cases in which such metals are employed, enables the discharge voltages hitherto required to be considerably reduced.

The invention will be more readily undcrstood by reference to the accompanyingr drawing, in which Fig. 1 shows a tube with the cathode in net form while the anode 1s 1n the form of a wire projecting into the hollow cathode.

Fig. 2 shows both the anode and the cathode each in the form of a net. This form of construction is especially adapted for use in connection with alternating currents in which case both electrodes become luminous.

In accordance with the invention the reduction of the discharge voltage is obtained by usiner metals of a specially high degree of purity or the cathode which, after they have been subjected to the manufacturing process-which may involve annealing or melting in a vacuum or in an indifferent atmosphereare almost free of gas. The de ee of subdivision of the metal of thel electrode should preferably besuch that the amount of gas that remains at the end of the manufacturing process is so small that even the last traces of it are capable of being removed from the tube, so that after the lamp is melted 0H the discharge of gas should not exceed the amount that can be removed by using the lamp for a short period` and through the automatic selfpurifying action of the electrodes and the gaseous contents which then takes place atV the desired low discharge volta-ge. a

The termina-l voltage with which this tube can be made to operate, de ends not'only on the material used for the e ectrodes, but also on the nature ot the gas. By using neon it is easy in this'way to reduce the terminal voltage to less than volts it very pure or substantiallychemically pure iron or tungsten wire is used tor the electrodes. By this means it is evenlpossible to reduce the terminal voltage to less than l0() volts so that tubes of this lrinol can be run oid' 110 volt supply mains. ll hlling ot argon, lrrypton and xenon are used the terminal voltages can be made still lower. This is the more remarkable because the drop of potential at a cathode of iron for example .in neon should, according to the present opinion of ex rts, be about volts. The necessary hig degree of subdivision of the matter, which in itself already contains very little gas, is most readily obtained by using woven or knitted metal netting, or coiled thin Wires or the like. The purification of these novel metalelectrodes, which are almost devoid of gas in any case, is accompllshed 1n accordance with the invention partly by filling the discharge tube with the aid of a pump with gas at the usual pressure (e. g. 10 mms. of argon or 10 mmsof neon) and then applying an excessive voltage, and finally pumping olf the gas fillin once or twice which has been made impure y the a plication of the excessive voltage, and part y by using the completed tube at the factory for a short time until the terminal voltage becomes constant.

The electrodes manufactured in accordance with the invention can also be advantageously employed in vacuum protective devices or vlightning arresters. By this means the arresters can be made to operate at the said low voltages. Previous attempts have been made to obtain the same result in vacuum arresters by using, in combination with a filling of noble gas, electrodes made of common metals which are easily volatilized by, and sensitive to, electric currents. Metals of this kind are alkali metals for instance or their alloys min ed with each other or with metals. But such metals are extremely inconvenient in theA process ot manufacturing the. tubes and yvery dangerous in use. llor this reason the substin tution ot these metals by metals which are much nobler and moreditlicult to melt, auch as tungsten or iron which,.in accordance with the invention, are rendered entr aordlm narily pure) constitutes aV considerable advance on account ofthe abovedescribed disadvantages being avoided.

With vacuum-arresters provided with electrodes according tothe invention and with a filling of noble gas a discharge voltage may be obtained which is 'almost as low as in the case of such electrodes made of alkali metal..

By using the novel electrodes4 in vacuum arresters the additionall advantage isv ob tained that the arresters operate noiselessly. llence their operation does not result in diam lat l lllllll chemically pure electrodes and by using care to have these electrodes free from oceluded and adsorbed gases, I obtain an electric vacuum tube which may be used to operate at avery low voltage.

10 I claimi- An electric' discharge device comprising a sealed container, an attenuated inert gas therein, non-alkaline electrodes therefor consistlng of line wire mesh free from oceluded non-inert' gases whereby a glow discharge lnay be operated between the electrodes at voltages of the order of one hundred volts, the area of said electrodes being great enough to permit of the indefinite continuance of such glow discharge at said voltage.

In testilnony whereof I affix my signature.

FRANZ SKAUPY. 

